America's millionaires are seeing their investments become a larger part of their overall wealth, but they still have difficulty opening up to their spouses about their financial dealings, said Jaki Boyer, senior wealth strategist for PNC Wealth Management.

As the economy and stock market have improved since the financial crisis, investments are increasing in share of wealth from 51% in 2012 to 63% today, according to PNC's latest survey of American millionaires. The survey also revealed that 85% of the respondents feel they currently have a greater sense of control over their financial future compared to 80% in 2014.

"After the market selloff in 2008 and 2009, people really tightened up and took a deeper look at the market and their holdings and that has given them more empowerment," said Boyer.

But while confidence among the millionaire class is growing, the survey showed that anxieties remain, with 55% being concerned with preserving their wealth, while 27% worried they won't be able to support the lifestyle they want for three decades or more in retirement.

Back on the positive side, the millionaire commitment to charitable giving is on the rise, with 97% giving to charitable organizations. Furthermore, 3 in 4 of them expect to give the same amount this year as last year, while 18% expect to give more.

"There are a lot of tax advantages to charitable giving, but the tax tail is not wagging the dog," said Boyer. "People really care about their community organizations."

When it comes to relationships, nearly 6 in 10 of those surveyed fully disclosed their financial situations before they got married or started living with their partner. But 3 in 10 did not discuss finances at all.

And in advance of Valentine's Day, it is worth noting that couples who fully disclosed their financial situations are more likely to pool their money. Roughly 9 in 10 said that conversations about their finances prior to getting married or living with their partner were helpful. Nearly 8 in 10 have never even thought about or considered a prenuptial agreement in their current relationship.

Also on the topic of love and millionaires, the survey showed that relationship tensions stem from contribution imbalance. While only 1 in 4 couples say they argue over money, those who do are more likely to be unequal contributors to the household finances and are less likely to have disclosed their finances before marriage or living together.